//#define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
#define rep(i, n) for(int i=0; i<n; ++i)
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
using namespace std;
using ll = int64_t;
using ld = long double;
using P = pair<int, int>;
using vs = vector<string>;
using vi = vector<int>;
using vvi = vector<vi>;
template<class T> using PQ = priority_queue<T>;
template<class T> using PQG = priority_queue<T, vector<T>, greater<T> >;
const int INF = 0xccccccc;
const ll LINF = 922337203685477580LL;
template<typename T1, typename T2>
inline bool chmax(T1 &a, T2 b) {return a < b && (a = b, true);}
template<typename T1, typename T2>
inline bool chmin(T1 &a, T2 b) {return a > b && (a = b, true);}
template<typename T1, typename T2>
istream &operator>>(istream &is, pair<T1, T2> &p) { return is >> p.first >> p.second;}
template<typename T1, typename T2>
ostream &operator<<(ostream &os, const pair<T1, T2> &p) { return os << p.first << ' ' << p.second;}

const int N = 1e3+10;

//head

int n, m;
string s, t;
int dp[N][N];

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cin >> n >> m;
  cin >> s >> t;
  rep(i, n+1) fill(dp[i], dp[i]+m+1, INF);
  dp[0][0] = 0;
  rep(i, n+1) rep(j, m+1) {
    if(i < n and j < m) {
      if(s[i] == t[j]) chmin(dp[i+1][j+1], dp[i][j]);
      else chmin(dp[i+1][j+1], dp[i][j]+1);
    }
    if(i < n) chmin(dp[i+1][j], dp[i][j]+1);
    if(j < m) chmin(dp[i][j+1], dp[i][j]+1);
    //cout << dp[i][j] << ' ' << i << ' ' << j << endl;
  }
  //rep(i, n+1) rep(j, m+1) cout << dp[i][j] << (j == m?'\n':' ');
  cout << dp[n][m] << endl;
}